Role of CEACAM1, ECM, and mesenchymal stem cells in an orthotopic model of human breast cancer

Generation, evolution, interfering factors, applications, and challenges of patient-derived xenograft models in immunodeficient mice

Establishing appropriate preclinical models is essential for cancer research. Evidence suggests that cancer is a highly heterogeneous disease. This follows the growing use of cancer models in cancer research to avoid these differences between xenograft tumor models and patient tumors. In recent years, a patient-derived xenograft (PDX) tumor model has been actively generated and applied, which preserves both cell-cell interactions and the microenvironment of tumors by directly transplanting cancer tissue from tumors into immunodeficient mice. In addition to this, the advent of alternative hosts, such as zebrafish hosts, or in vitro models (organoids and microfluidics), has also facilitated the advancement of cancer research. However, they still have a long way to go before they become reliable models. The development of immunodeficient mice has enabled PDX to become more mature and radiate new vitality. As one of the most reliable and standard preclinical models, the PDX model in immunodeficient mice (PDX-IM) exerts important effects in drug screening, biomarker development, personalized medicine, co-clinical trials, and immunotherapy. Here, we focus on the development procedures and application of PDX-IM in detail, summarize the implications that the evolution of immunodeficient mice has brought to PDX-IM, and cover the key issues in developing PDX-IM in preclinical studies.

Calcein Binding to Assess Mineralization in Hydrogel Microspheres

We describe a method to assess mineralization by osteoblasts within microspheres using calcein. Fluorescence imaging of calcein bound to the calcium in hydroxyapatite permits assessment of the mineralized portion of the extracellular matrix. Colorimetric imaging of Alizarin Red S complexed with calcium also gives measures of mineralization, and in tissue cultures calcein and Alizarin Red S have been shown to bind to the same regions of mineral deposits. We show that when the mineralization takes place within hydrogel microspheres, Alizarin Red S does not stain mineral deposits as consistently as calcein. As tissue engineers increasingly encapsulate osteoprogenitors within hydrogel scaffolds, calcein staining may prove a more reliable method to assess this mineralization.

Three-Dimensional Porous Trabecular Scaffold Exhibits Osteoconductive Behaviors In Vitro

In the USA, approximately 500,000 bone grafting procedures are performed annually to treat injured or diseased bone. Autografts and allografts are the most common treatment options but can lead to adverse outcomes such as donor site morbidity and mechanical failure within 10 years. Due to this, tissue engineered replacements have emerged as a promising alternative to the biological options. In this study, we characterize an electrospun porous composite scaffold as a potential bone substitute. Various mineralization techniques including electrodeposition were explored to determine the optimal method to integrate mineral content throughout the scaffold. In vitro studies were performed to determine the biocompatibility and osteogenic potential of the nanofibrous scaffolds. The presence of hydroxyapatite (HAp) and brushite throughout the scaffold was confirmed using energy dispersive X-ray fluorescence, scanning electron microscopy, and ash weight analysis. The active flow of ions via electrodeposition mineralization led to a threefold increase in mineral content throughout the scaffold in comparison to static and flow mineralization. Additionally, a ten-layer scaffold was successfully mineralized and confirmed with an alizarin red assay. In vitro studies confirmed the mineralized scaffold was biocompatible with human bone marrow derived stromal cells. Additionally, bone marrow derived stromal cells seeded on the mineralized scaffold with embedded HAp expressed 30% more osteocalcin, a primary bone protein, than these cells seeded on non-mineralized scaffolds and only 9% less osteocalcin than mature pre-osteoblasts on tissue culture polystyrene. This work aims to confirm the potential of a biomimetic mineralized scaffold for full-thickness trabecular bone replacement.

The effect of low-magnitude, high-frequency vibration on poly(ethylene glycol)-microencapsulated mesenchymal stem cells

Low-magnitude, high-frequency vibration has stimulated osteogenesis in mesenchymal stem cells when these cells were cultured in certain types of three-dimensional environments. However, results of osteogenesis are conflicting with some reports showing no effect of vibration at all. A large number of vibration studies using three-dimensional scaffolds employ scaffolds derived from natural sources. Since these natural sources potentially have inherent biochemical and microarchitectural cues, we explored the effect of low-magnitude, high-frequency vibration at low, medium, and high accelerations when mesenchymal stem cells were encapsulated in poly(ethylene glycol) diacrylate microspheres. Low and medium accelerations enhanced osteogenesis in mesenchymal stem cells while high accelerations inhibited it. These studies demonstrate that the isolated effect of vibration alone induces osteogenesis.

RNA-based TWIST1 inhibition via dendrimer complex to reduce breast cancer cell metastasis

Breast cancer is the leading cause of cancer-related deaths among women in the United States, and survival rates are lower for patients with metastases and/or triple-negative breast cancer (TNBC; ER, PR, and Her2 negative). Understanding the mechanisms of cancer metastasis is therefore crucial to identify new therapeutic targets and develop novel treatments to improve patient outcomes. A potential target is the TWIST1 transcription factor, which is often overexpressed in aggressive breast cancers and is a master regulator of cellular migration through epithelial-mesenchymal transition (EMT). Here, we demonstrate an siRNA-based TWIST1 silencing approach with delivery using a modified poly(amidoamine) (PAMAM) dendrimer. Our results demonstrate that SUM1315 TNBC cells efficiently take up PAMAM-siRNA complexes, leading to significant knockdown of TWIST1 and EMT-related target genes. Knockdown lasts up to one week after transfection and leads to a reduction in migration and invasion, as determined by wound healing and transwell assays. Furthermore, we demonstrate that PAMAM dendrimers can deliver siRNA to xenograft orthotopic tumors and siRNA remains in the tumor for at least four hours after treatment. These results suggest that further development of dendrimer-based delivery of siRNA for TWIST1 silencing may lead to a valuable adjunctive therapy for patients with TNBC.

Signaling by epithelial members of the CEACAM family - mucosal docking sites for pathogenic bacteria

Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) comprise a group of immunoglobulin-related vertebrate glycoproteins. Several family members, including CEACAM1, CEA, and CEACAM6, are found on epithelial tissues throughout the human body. As they modulate diverse cellular functions, their signaling capacity is in the focus of current research. In this review we will summarize the knowledge about common signaling processes initiated by epithelial CEACAMs and suggest a model of signal transduction by CEACAM family members lacking significant cytoplasmic domains. As pathogenic and non-pathogenic bacteria exploit these receptors during mucosal colonization, we try to highlight the connection between CEACAMs, microbes, and cellular responses. Special emphasis in this context is placed on the functional interplay between CEACAMs and integrins that influences matrix adhesion of epithelial cells. The cooperation between these two receptor families provides an intriguing example of the fine tuning of cellular responses and their manipulation by specialized microorganisms.

Carcinoembryonic antigen-related cell adhesion molecule 1 negatively regulates granulocyte colony-stimulating factor production by breast tumor-associated macrophages that mediate tumor angiogenesis

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a cell adhesion molecule expressed on epithelial cells and activated immune cells, is downregulated in many cancers and plays a role in inhibition of inflammation in part by inhibition of granulocyte colony-stimulating factor (G-CSF) production by myeloid cells. As macrophages are associated with a poor prognosis in breast cancer, but play important roles in normal breast, we hypothesized that CEACAM1 downregulation would lead to tumor promotion under inflammatory conditions. Cocultures of proinflammatory M1 macrophages with CEACAM1 negative MCF7 breast cells produced high levels of G-CSF (10 ng/mL) compared to CEACAM1-transfected MCF7/4S cells (1 ng/mL) or anti-inflammatory M2 macrophage cocultures (0.5 or 0.1 ng/mL, MCF7 or MCF7/4S, respectively). The expression of CEACAM1 on M1s was much greater than for M2s and was observed only in cocultures with either MCF7 or MCF7/4S cells. When M1 macrophages were mixed with MCF7 cells and implanted in murine mammary fat pads of nonobese diabetic/severe combined immunodeficient mice, tumor size and blood vessel density were significantly greater than MCF7 or MCF7/4S only tumors which were hardly detected after 8 weeks of growth. In contrast, M1 cells had a much reduced effect on MCF7/4S tumor growth and blood vessel density, indicating that the tumor inhibitory effect of CEACAM1 is most likely related to its anti-inflammatory action on inflammatory macrophages. These results support our previous finding that CEACAM1 inhibits both G-CSF production by myeloid cells and G-CSF-stimulated tumor angiogenesis.